Browsing by Author "Castro, J"

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    Air-pollution modelling in an urban area: Correlating turbulent diffusion coefficients by means of an artificial neural network approach
    (PERGAMON-ELSEVIER SCIENCE LTD, 2006) Perez Roa, R; Castro, J; Jorquera, H; Perez Correa, JR; Vesovic, V
    The vertical pollutant dispersion is quite sensitive to the eddy diffusivity, K-V. Therefore, good estimations of K-V are essential for improving the predictive performance of Eulerian dispersion models; especially in urban areas where literature based K-V correlations are not always accurate. Here, we present a methodology to obtain a more accurate, but site-specific, Kv correlation. It is based on using artificial neural networks (ANN) to find the best Kv function for a particular urban area by minimizing, in a least-squares sense, the difference between ambient measurements of carbon monoxide and dispersion simulations of this tracer species. The resulting ANN-K-V correlation is a function of three parameters namely, the stability parameter (z/L), the height within the mixing layer (z/h), and the scaled height (zf(C)/u(*))-hence the Monin-Obukhov (L), mixing (h) and Ekman (u(*)/f(C)) lengths are used to predict Kv across the atmospheric boundary layer.
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    Protein(s) from the gram-positive bacterium Clavibacter michiganensis subsp. michiganensis induces a hypersensitive response in plants
    (1998) Alarcón, C; Castro, J; Muñoz, F; Arce-Johnson, P; Delgado, J
    The gram-positive tomato pathogen Clavibacter michiganensis subsp. michiganensis induced a local necrotic response on four-o'clock (Mirabilis jalapa) and tobacco (Nicotiana tabacum) plants. This necrosis response was characteristic of the hypersensitive response (HR). The cell-free culture supernatant from strain CMM623 also induced a necrosis that was phenotypically similar to that induced by the bacteria. Inhibitors of plant metabolism suppressed the necrotic reaction of both M. jalapa and tobacco. The HR-inducing activity present in the supernatant was heat stable, sensitive to proteases; and had hn apparent molecular mass in the range of 35 to 50 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The properties observed for the necrosis-inducing activity resembled bacteria.
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    Relevance of Niemann-Pick type C1 protein expression in controlling plasma cholesterol and biliary lipid secretion in mice
    (WILEY, 2002) Amigo, L; Mendoza, H; Castro, J; Quinones, V; Miquel, JF; Zanlungo, S
    Receptor-mediated endocytosis is one of the major mechanisms for uptake of lipoprotein cholesterol in the liver. Because Niemann-Pick C1 (NPC1) protein is a key component in the intracellular distribution of cholesterol obtained from lipoproteins by the endocytic pathway, it may play a critical role in controlling plasma lipoprotein cholesterol and its biliary secretion. A murine model of Niemann-Pick type C disease (NPC), the NPC1-deficient [NPC1 (- / -)] mouse, was used to evaluate the relevance of hepatic NPC1 expression in regulating plasma lipoprotein cholesterol profile and biliary lipid secretion under chow and high-cholesterol diets. Total plasma cholesterol concentrations were increased in NPC1 (- / -) mice compared with wild-type mice when both mouse strains were fed chow or high-cholesterol diets. The increased plasma cholesterol levels found in NPC1 (- / -) mice were mostly due to elevated cholesterol content in larger and more heterogeneous HDL particles. On the chow diet, biliary lipid secretion was not impaired by NPC1 deficiency. Furthermore, chow-fed NPC1 (- / -) mice showed a small, but significant, increase in biliary cholesterol secretion. On the high-cholesterol diet, wild-type mice increased biliary cholesterol output, whereas NPC1 (- / -) mice did not. Finally, hepatic NPCI overexpression by adenovirus-mediated gene transfer increased biliary cholesterol secretion by 100% to 150% in both wild-type mice and cholesterol-fed NPC1 (- / -) mice. In conclusion, hepatic NPC1 expression is an important factor for regulating plasma HDL cholesterol levels and biliary cholesterol secretion in mice.